Jean-Paul Charles Aymard Sartre (French pronunciation: , English: /ˈsɑrt/; 21 June 1905 – 15 April 1980) was a French existentialist philosopher, playwright, novelist, screenwriter, political activist, biographer, and literary critic. He was one of the leading figures in 20th century French philosophy and Existentialism, and his work continues to influence further fields such as sociology and literary studies.

Jean-Paul Sartre was born and raised in Paris to Jean-Baptiste Sartre, an officer of the French Navy, and Anne-Marie Schweitzer. His mother was of Alsatian origin, and the first cousin of Nobel Prize laureate Albert Schweitzer. (Her father, Charles Schweitzer, 1844-1935, was the older brother of Albert Schweitzer's father, Louis Théophile, 1846-1925). When Sartre was 15 months old, his father died of a fever. Anne-Marie raised him with help from her father, Charles Schweitzer, a high school professor of German, who taught Sartre mathematics and introduced him to classical literature at a very early age. As a teenager in the 1920s, Sartre became attracted to philosophy upon reading Henri Bergson's Essay on the Immediate Data of Consciousness. He studied and earned a doctorate in philosophy in Paris at the elite École Normale Supérieure, an institution of higher education that was the alma mater for several prominent French thinkers and intellectuals. Sartre was influenced by many aspects of Western philosophy, absorbing ideas from Kant, Hegel, Husserl and Heidegger, among others. In 1929 at the École Normale, he met Simone de Beauvoir, who studied at the Sorbonne and later went on to become a noted philosopher, writer, and feminist. The two became inseparable and lifelong companions, initiating a romantic relationship, though they were not monogamous. Sartre served as a conscript in the French Army from 1929 to 1931 and he later argued in 1959 that each French person was responsible for the collective crimes during the Algerian War of Independence.

Together, Sartre and de Beauvoir challenged the cultural and social assumptions and expectations of their upbringings, which they considered bourgeois, in both lifestyle and thought. The conflict between oppressive, spiritually-destructive conformity (mauvaise foi, literally, "bad faith") and an "authentic" way of "being" became the dominant theme of Sartre's early work, a theme embodied in his principal philosophical work L'Être et le Néant (Being and Nothingness) (1943). Sartre's introduction to his philosophy is his work Existentialism is a Humanism (1946), originally presented as a lecture.